Motor Speed Reduction

[Willyou]

With all this effort, why don't you just purchase a heater with a blower?

It is. It just needed replacing and I had this one on hand. It would hardly be any effort at all if I just knew what works vs what to avoid. I could also just buy a slower motor perhaps. Just trying to use what I have.

[daddo]

Sorry. I should have been more clear. The motor no longer has the centrifugal (squirrel cage) blower. It now has an approx. 8" dia axil fan mounted to it. Given the overall configuration of the heater box, I could probably restrict the outflow with a grill of some sort. A controller, if it works, will also quiet it down somewhat which would be a nice additional benefit. Lacking that, I'll do some experimenting with some grill work.

This is the (or similar) motor I'm asking about:
https://www.supplyhouse.com/Fasco-A200-1...Motor-115V

 Restricting the air on that type of open fan can cause an amperage gain. Test it first.

 Be sure the fan blade is rated for that speed. Changing the specs on a motors required purpose by using a different type blade may or may not work. (Blade pitch, rpms, HP/wattage, cfm, voltage..blah blah blah)

 Creating a possible higher load then dropping voltage is going to be an interesting..... "Experiment".

Go for it.

[Roly]

 Restricting the air on that type of open fan can cause an amperage gain. Test it first.

 Be sure the fan blade is rated for that speed. Changing the specs on a motors required purpose by using a different type blade may or may not work. (Blade pitch, rpms, HP/wattage, cfm, voltage..blah blah blah)

 Creating a possible higher load then dropping voltage is going to be an interesting..... "Experiment".

Go for it.

Keep a close eye on motor temperature.   Normally you have to drop load when dropping voltage on a induction motor or it will overheat.  Roly

[Willyou]

Keep a close eye on motor temperature.   Normally you have to drop load when dropping voltage on a induction motor or it will overheat.  Roly

That is an interesting point. However, I don't anticipate doing both. I'll try adding load first but, if I find that I can reduce the rpm, I won't need or want the added load.

[daddo]

You do realize that slowing the motor won't give you more heat, if that's your goal- it will just make the air feel hotter when you stand in front of it. The heat strips are still producing xxx btu's no matter what speed the motor. In other words, it's not going to heat the space more. In fact, the heater coils will last longer running a bit cooler.

[Willyou]

Yes. I'm aware that I won't get more heat. This motor runs at a higher rpm than the original and I'm trying to cut down on the air blast and the noise. Just need enough flow for good circulation in the small shop (16x20).
I put a dimmer stitch on it and it works. Ran it for about 30 min and the motor stayed cool. Speed graduations are not real smooth but, that doesn't really matter as I'll find a speed I like and leave it there. Maybe a better quality dimmer would do a better job but, again, it doesn't matter too much.

[TDKPE]

This is the (or similar) motor I'm asking about:
https://www.supplyhouse.com/Fasco-A200-1...Motor-115V

The one in the link is a shaded-pole motor, with a single synchronous speed.  Versions with multiple speeds are usually the same (single speed) but they reduce the number of turns in the winding to reduce its torque, and with a fan for a load, reduced torque results in reduced speed and noise.  Like a table fan.  

Reducing the current via a motor-rated 'dimmer' switch is usually not going to hurt it.  It's how things like bathroom and kitchen fans with a continuously variable speed control work.

[Willyou]

The one in the link is a shaded-pole motor, with a single synchronous speed.  Versions with multiple speeds are usually the same (single speed) but they reduce the number of turns in the winding to reduce its torque, and with a fan for a load, reduced torque results in reduced speed and noise.  Like a table fan.  

Reducing the current via a motor-rated 'dimmer' switch is usually not going to hurt it.  It's how things like bathroom and kitchen fans with a continuously variable speed control work.

Thanks for the info.  I suspect the dimmer I'm using is just a light dimmer. It's an old one I had in my junk box. I'll look for a motor speed control similar to the one I cited in my original post.